This invention relates in general to static seals and more particularly to a gasket employed for sealing between components in a fuel cell.
A fuel cell is an electrochemical energy converter that includes two electrodes placed on opposite surfaces of an electrolyte. In one form, an ion-conducting polymer electrolyte membrane is disposed between two electrode layers (also sometimes called gas diffusion layers), with layers of a catalyst material between the membrane and the electrode layers, to form a membrane electrode assembly (MEA). The MEA is used to promote a desired electrochemical reaction from two reactants. One reactant, oxygen or air, passes over one electrode while hydrogen, the other reactant, passes over the other electrode. The oxygen and hydrogen combine to produce water, and in the process generate electricity and heat.
An individual cell within a fuel cell assembly includes a MEA placed between a pair of separator plates (also sometimes called flow field plates). The separator plates are typically fluid impermeable and electrically conductive. Fluid flow passages or channels are formed adjacent to each plate surface at an electrode layer to facilitate access of the reactants to the electrodes and the removal of the products of the chemical reaction.
In such fuel cells, resilient gaskets or seals are typically provided between the faces of the MEA and the perimeter of each separator plate to prevent leakage of the fluid reactant and product streams. Since the fuel cell operates with oxygen and hydrogen, it is important to provide a seal that not only seals well against hydrogen, oxygen and water, but that will seal well as the temperature changes due to the heat that is given off during fuel cell operation. To assure a good seal, the seals need to be formed accurately as well as aligned properly with the other components. In particular, the gaskets can be difficult to assemble into a cell because they are flexible and may have a tendency to bend or twist. This can make proper alignment of the cell components time consuming and prone to misassembly. Moreover, in order to assure a good seal around the entire gasket, a certain amount of force (a sealing force) is applied to hold the separator plates against the gaskets. But this may cause portions of the gasket to be pressed into the fluid flow channels of the separator plates, which restricts the flow channels in the separator plates.
Thus, it is desirable to have a gasket of an individual cell of a fuel cell that is relatively easy to align during an assembly operation while assuring the proper sealing for the finished assembly, and which will not interfere with the flow channels in the separator plate.